What happens if you try to freeze water in an water tight container If I have a container that is full of water and I attempt to freeze the water by freezing the container, what would happen if the container is strong enough to prevent the water expansion? Could the water be in liquid state even though it is at or below freezing point?
This is probably a daft question but its something that's been bugging me.
 A: In order to keep the density of water at 1kg/litre as you decrease its temperature below 0 centigrade you would need a container that remained rigid at many thousands of atmospheres pressure. The water would then remain liquid until something like -20 degrees centigrade. 
At still lower temperatures it would become solid, but it would not form crystalline ice which always has a density lower than 1kg/litre. Instead it would form a glassy solid known as amorphous ice which has a higher density under such pressures.
There are several high density phases of amorphous ice and to get the exact details of which phase it would pass through you need a phase diagram showing density as a function of temperature and pressure extending to very high pressures and low temperatures. You can then follow the contour corresponding to a density of 1kg/litre to see how the pressure and phase would vary as the temperature decreased. I can only find enough information to give the vague answer above and it is possible that the diagram is not known well enough yet to say much more.
A: Yes, of course, the freezing point will decrease by the pressure 
developed, while part of the water freezes. 
But do not underestimate the pressures! In such an experiment 
easily some thousand bares may be developed. (Depends on the 
rigidity of the vessel and the volume of water) 
Here is a video showing how freezing water cracks a cast iron sphere.
(The bath is ice/salt at about -10°C)
A: I think what you are really getting at is the nature of phase changes in respect of changes in pressure, volume and temperature. This 3D diagram explains a lot though it can a while to interpret it.
And the associated article should explain in more detail. Here is also a simpler 2D version.
A: I think that increase in pressure highers the freezing point of water from 0 degrees -ve thes the water will still freeze but at a lower temperature
